Herbicide



United States Patent HERBICIDE William T. Dye, Jr.,-Decatur, Ala., assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application October 20, 1955, Serial No. 541,842

6 Claims. (Cl. 71-23) The present invention relates to nitrogenous organic compounds of phosphorus, and more particularly provides useful new nitrogenous phosphonium halides, and herbicidal compositions containing the same.

According to the invention there are provided benzyltris(dialkylamino)phosphonium halides having the general formula R NY:

Dem-1 R 1/ NY,

in which R and R are selected from the class consisting of hydrogen, chlorine, bromine and alkyl radicals of from 1 to 18 carbon atoms, Y is selected from the class consisting of alkyl radicals of from 1 to 4 carbon atoms and X is selected from the class consisting of bromine and chlorine.

Compounds having the above general formula are readily obtained by contacting a hexaalkylphosphorus triamide in which the alkyl radical has from 1 to 4 carbon atoms with a benzyl halide selected from the class consisting of benzyl chloride and benzyl bromide and the nuclear chloro-, bromo-, dichloro-, dibromo-, chlorobromo-, alkyl-, dialkyl-, chloroalkyl-, or bromoalkyl-derivatives of such benzyl halides, substantially according to the scheme:

R NY: R NY:

-e R N Y, R 1/ NY:

in which R, R, Y and X are as defined above.

Benzyl halides useful for the present purpose include, e. g., benzyl chloride, benzyl bromide, 2-,'3- or 4-chlorobenzyl chloride, 2-, 3- or 4-bromobenzyl chloride, 2-, 3- or 4-chlorobenzyl bromide, 2-, 3- or 4-bromobenzyl bromide, 2,3-dichlorobenzyl chloride, 3,5-dibromobenzy1 chloride, 3,4-dichlorobenzyl bromide, 2,4-dibromobenzyl bromide, 2-chloro-3-bromobenzyl chloride, 2-chloro-5- bromobenzyl bromide, 2-, 3-, or 4-ethylbenzyl bromide, 2-methyl-4-chlorobenzyl chloride, 3,3-diamylbcnzyl chloride, 2-, 3-, or 4-amylbenzyl chloride, 4-hexylbenzyl chloride, 2-heptylbenzyl chloride, 4-(2-ethylhexyl)benzyl chloride, 3-n-octylbenzyl bromide, a nonylbenzyl chloride in which the nonyl radical is derived from propylene trimer, Z-n-decylbenzyl chloride, 2-, 3-, or 4-dodecylbenzyl chloride, ar-dodecyl-ar-methylbenzyl bromide, artetradecyibenzyl chloride, an ar-tridecylbcnzyl chloride in whichthe tridecyl radical is derived by chlorination of an alcohol obtained according to the 0x0 process by the pressure reaction of carbon monoxide and hydrogen with a higher olefin, ar-hexadecylbenzyl chloride, 2-, 3-, or 4-n-octadecylbenzyl chloride, etc.

Hexaalkylphosphorus triamides which may be reacted with the benzyl halides to yield the present benzyltris(dialkylamino)phosphonium halides include, e. g., hexamethylphosphorous triamide, hexaethylphosphorous triamide, heXa-n-propylphosphorous triamide, hexaisopro- 2 pylphosphorus triamide, hexa-n-butylphosphorous triamide, etc.

As illustrative of benzyltris(dialkylamino)phosphonium halides provided by the invention may be mentioned, e. g., benzyltris(dimethylamino)phosphonium chloride or bromide, benzyltris(diethylamino)phosphonium chloride or bromide, benzyltris(di-n-butylamino)phosphonium chloride or bromide, 2-chlorobenzyltris(diisopropylamino)phosphonium chloride or bromide, 3-bromobenzyltris(diethylamino)phosphonium chloride or bromide, 4- chlorobenzyltris(dimethylamino)phosphonium chloride or bromide, 2,3-dichlorobenzyltris(dimethylamino)phosphonium chloride or bromide, 3,4-dibromobenzyltris(di-nproplyamino)phosphonium chloride or bromide, 2-chloro- 4-bromobenzyltris(dimethylamino)phosphonium chloride or bromide, 4-ethylbenzyltris(diethylamino)phosphonium chloride or bromide, 2-methyl-4-chlorobenzyltris(di-nbutylamino)phosphonium chloride or bromide, ar-diamylbenzyltris(dimethylamino)phosphonium chloride or bromide, 2-, 3-, or 4-amylbenzyltris(dimethylamino)- phosphonium chloride .or bromide, 3-(2-ethylhexyl)benzyltris(dimethylamino)phosphonium chloride or bromide, ar nonylbenzyltris(dimethylamino)phosphonium chloride or bromide, 2-, 3-, or 4-decylbenzyltris(dimethylamino)phosphonium chloride or bromide, 4-undecylbenzyltris(dimethylamino)phosphonium chloride or bromide, an ar-tertor n-dodecylbenzyltris(dimethylamino)- phosphonium chloride prepared from hexamethylphosphorous triamide and an ar-tertor n-dodecyl chloride obtained by chloromethylation of an ar-dodecylbenzene by a method known to give substitution of the chloromethyl group in the aromatic nucleus, 2-, 3-, or 4-tetradecylbenzyltris(dimethylamino)phosphonium chloride or bromide,

. 2-, 3-, or 4-octadecylbenzyltris(dimethylamino)phosphonium chloride or bromide, etc.

As employed throughout the specification and claims, the term ar designates substitution of the radical which it prefixes at an uncertain position at an aromatic ring carbon.

Reaction of the benzyl halide compound with the hexaalkylphosphorous triamide to yield the present phosphonium halides is elfected by simply mixing the two reactants in the presence or absence of an inert solvent or diluent at ordinary or increased temperature, depending upon the nature of the individual reactant. While reaction of the triamides with the benzyl halides occurs in the presence or absence of a diluent, it is often advantageous to use an inert solvent or diluent. The use of such an inert extraneous material serves to effect smooth reaction and to facilitate separation of the crystalline phosphonium halides. Although any inert liquid material may be used for this purpose, I prefer to employ as diluent a liquid which is not only inert under the reaction conditions, but which is also a solvent for one or, preferably, both reactants and a comparative nonsolvent for the phosphonium halide. Dioxane is admirably suited to this purpose. The phosphonium halides are well-defined high-melting crystalline compounds. Most of the present compounds are stable under ordinary atmospheric conditions; some of them, however, have a tendency to deliquesce under moist or humid conditions. Their deliquescence decreases with increasing purity. They are generally soluble in water, hot dioxane, chloroform, and ethanol, but insoluble in ether, hexane and benzene.

The present benzyl phosphonium halides are valuable for a variety of industrial and agricultural purposes. They are generally good biological toxicants, being useful as herbicides, fungicides, insecticides and nematocides. The biological toxicant efficiency of the present compounds is demonstrated when they are employed in very low concentrations. Since they are generally water-soluble no expensive or obnoxious carriers need be employed in the formulation of herbicidal, fungicidal or insecticidal compositions containing the ,present compounds as the active ingredients. Being crystalline solids, the .present compounds may be also incorporated into powders such as pumice, clay, bentonite, etc., .in the formulation-of toxicanhdusts.

This invention is further illustrated, but not limited, by the following examples:

Example I Found Calcd. for

CuHgBNaPC] PercentCl 11.87 12.23 PercentN "14.63 '14. 51

Example 2 A mixture consisting of 25.8 g. Z-chlorobenzyl chloride and 25.4 -g. hexamethylphosphorous ,triamide dissolved in 200 cc. ether was allowed to stand for 3 weeks at ordinew mom temp ra ,The need es w re filtered .ofi, rinsed with dioxane, then dissolved in chloroform and reprecipitated from hot dioxane. The resulting slurry of fine crystals was then filtered, rinsed with dioxane and dried. There was thus obtained 12.3 g. of the substan tially pure 2-chlorobenzyltris(dimethylamino)phosphoniurn chloride, M. P. 2345.5 C. and analyzing as follows:

Found Calcd. for

CgHgtNaPClz Percent Ionic chlorine 11. 28 10. 93 Percent Total chlorine 21. 02 21. 87 Percent N 12. 99 12. 96

Example 3 A mixture consisting of 40.7 g. hexamethylphosphorous triamide, 40.3 g. 2-chlorobenzyl chloride and 200 cc. dry dioxane was refluxed, with stirring, for 7 hours, 200 cc. dioxane was then added to the reaction mixture and the whole was allowed to stand overnight. The white prisms were filtered, dissolved in hot chloroform, precipitated with dioxane, and dried, yielding 60 g. (74% of theoretical yield) of Z-chlorobenzyltris(dimethylamino)phosphonium chloride, M. P. 233.5 C.

Example 4 24.7 g. hexaethylphosphorous triamide, 29.2 g. 3,4-dichlorobenzyl chloride and 100 cc. sodium dried dioxane were mixed and heated to gentle reflux. After refluxing for five hours without precipitation, the mixture was allowed to stand overnight, during which time elongated platelets precipitated. These were filtered and washed, first with dioxane and then with ether; M. P. 140-160" C. Two repeated recrystallizations from dioxane and ether gave 22.5 g. crude 3,4dichlorobenzyltris(diethylamino)phosphonium chloride, M. P. 145160 C.

Example 5 A mixture consisting of 40.7 g. hexamethylphosphorous triamide, 40.3 g. freshly distilled 4-chlorobenzyl chloride and cc. dry dioxane was refluxed for 3 hours, then diluted to 400 cc. with dioxane and allowed to cool. The crystals were filtered off and recrystallized twice from chloroform and dioxane, yielding 46 g. of the substantially pure 4-chlorobenzyltris'(dimethylamino)phosphonium chloride, M. P. 2l1-.-2 C.

Example 6 31.4 g. 3,4-dichlorobenzyl chloride was mixed with 25.4 g. hexamethylphosphorous triamide in a dropping funnel; and the mixture .was introduced, dropwise, into a flask which was immersed in a bath held at a temperature of C. The mixture in the funnel began to precipitate even before all of it had been introduced into the flask. After all of the mixture had been added, the contents of the flask were heated for 15 minutes at 120 C.,:then cooled to 100 C. and diluted with 50 cc. dioxane. The whole was thencooled and further diluted with ether. Filtration gave 40 g. .of a light tan product, I. 190230 C. This was recrystallized from hot chlong; form and dioxane to yield 30 -g. of pure white prisms of 3,4-dichlorobenzyltris(dimethylamino)phosphonium chlo- Into a 250 ml. flask there were placed 98.3 g. (0.33 mole) of ar-dodecylbenzyl chloride and 54.3 g. (0.33 mole) of hexamethylphosphorous triamide. The ardodecylbenzyl chloride was prepared by chloromethylation of an ar-dodecylbenzene employing the method described in the Raterink U. S. Patent No. 2,630,459 for introducing a chloromethyl group into the aromatic nucleus. The mixture was swept with nitrogen and heated with stirring to 100-120 C., whereupon the reaction became exothermic so that a temperature of about 170 C. was obtained. External cooling was used to reduce the temperature of the reaction mixture to 140 C., and heating with stirring at this temperature was continued for an additional hour. The resulting reaction mixture, partly crystalline and semi-solid, comprised the substantially pure ar-dodecylbenzyltris(dimethylamino)phosphonium chloride analyzing 7.81% ionicchlorine, as against 7.75%, the calculated value.

Example 9 A mixture consisting of 61.8 g. (0.2 mole) of ar-dodecyl-ar-methylbenzyl chloride (obtained from ar-dodecyltoluene by the chloromethylating procedure described in Example 8) and 32.6 g. (0.2 mole) of hexamethylphosphorous triamide was heated with stirring to a temperature of 120 C., external cooling was applied and heating was continued to a temperature of 135-140 C. for an additional hour. At the end of this time cooling Was discontinued and the reaction mixture was heated at -155 C. for an additional two hours. The resulting reaction comprised the substantially pure ar-dodecylar-methylbenzyltris (dimethylamino) phosphonium chloride, a semi-fluid material, which analyzed as follows:

Example Herbicidal spray testing of the benzyltris(dimethylamino) phosphoniurn chloride of Example 1 was conducted as follows:

A cyclohexanone solution of the compound was prepared and this solution and an emulsifying agent was added to water, the quantity of solution employed being calculated to give respective emulsions containing 1.0% and 0.3 of the chloride based on the weight of the total emulsion. The quantity of emulsifying agent used was 0.2% by weight based on the weight of the total emulsion and the emulsifying agent which was used was Emulsifier L (a mixture of a polyalkylene derivative and an alkylbenzene-sulfonate). Three-week-old corn and bean plants respectively were sprayed with said emulsions, two plants of each variety being employed. The spraying was continued until droplets formed on and/or fell from the foliage and stems of the sprayed plants, up to ml. of the emulsions being applied to each plant. The sprayed plants as well as two untreated blank specimens of each plant were then allowed to remain under standard conditions of sunlight and watering for a period of one week. At the end of this time, observation of the plants showed that those of the bean plants which had been sprayed with either the 1.0% or the 0.3% emulsion of the chloride were dead and completely defoliated, that com plants which had been sprayed with the 1.0% emulsion of the chloride were dead with the foliage thereof completely dried, and that com plants which had been sprayed with the 0.3% emulsion of the chloride were severely injured.

Example 1] Example 12 A flat containing about two plants each of two-weekold wild oats, cheat grass, rye grass, buckwheat, red clover, mustard, beet, cotton and cucumber, and five plants of corn was employed in the herbicidal testing of ar-dodecyl-ar methylbenzyltris (dimethylamino) phosphonium chloride of Example 9. A herbicidal spray was prepared by dissolving the chloride in acetone and adding the resulting acetone solution to water in a quantity to make up a 1.0% concentration of said chloride. The flat of plants was sprayed with the resulting solution to run 01f. The sprayed fiat was then placed in the greenhouse under ordinary conditions of sunlight and watering for ten days. Observation of the plants at the end ofthis time showed that those of the broad-leaf plants which had been sprayed with said solution were completely dead and that the narrow-leaf plants were moderately injured. Plan-ts in a blank fiat which had been kept in the greenhouse under the same conditions were all thriving.

This is a continuation-in-part of my copending application, Serial No. 485,585, filed February 1, 1955, now Patent No. 2,730,547.

What I claim is:

l. The method of destroying undesirable plants which comprises applying to the plants a toxic quantity of a herbicidal composition comprising asthe efiective ingredient a phosphonium halide of the formula R IIIY:

CHr-P-NY1 in which R and R are selected from the class consisting of hydrogen, chlorine, bromine and alkyl radicals of from 1 to 18 carbon atoms, Y is selected from the class con sisting of alkyl radicals of from 1 to 4 carbon atoms, and X is selected from the class consisting of chlorine and bromine.

2. The method of destroying undesirable plants which comprises applying to the plants a toxic quantity of a herbicidal composition comprising as the elfective ingredient an alkylbenzyltris(dimethylamino)phosphonium chloride having from 1 to 18 carbon atoms in the alkyl radical.

3. The method of destroying undesirable plants which comprises applying to the plants a toxic quantiy of a herbicidal composition comprising as the effective ingredient a chlorine-substituted benzyltris (dimethylamino) phosphonium chloride in which there are present from 1 to 2 chlorine substituents in the aromatic ring.

4. The method of destroying undesirable plants which comprises applying to the plants a toxic quantity of a herbicidal composition comprising benzyltris(dimethylamino)phosphonium chloride as the active ingredient.

5. The method of destroying undesirable plants which comprises applying to the plants a toxic quantity of a herbicidal composition comprising ar-dodecyl-ar-methylbenzyltris(dimethylarnino)phosphonium chloride.

6. The method of destroying undesirable plants which comprises applying to the plants a toxic quantiy of a herbicidal composition comprising 2,4-dich1orobenzyltris (dimethylamino)phosphonium chloride.

No references cited. 

1. THE METHOD OF DESTROYING UNDESIRABLE PLANTS WHICH COMPRISES APPLYING TO THE PLANTS A TOXIC QUANTITY OF A HERBICIDAL COMPOSITION COMPRISING AS THE EFFECTIVE INGREDIENT A PHOSPHONIUM HALIDE OF THE FORMULA 